1. Field of the Invention
The invention relates to a universal test system capable of controlling a plurality of parameters relating to the operation of display devices for presenting optoelectronic information of various types. It applies both to screen displays, for example with a cathode tube (CRT), with liquid crystals (LCD), or even with a plasma and to devices in which the image is projected to infinity such as for example Head Up Displays (HUD), display systems by projection on the windscreen or even Helmet Mounted Displays (HMD).
More particularly, the object of the invention is to allow a characterization of these information presentation devices, by means of a single sensor easy to use and allowing the whole of the measurements and tests required for this characterization to be carried out in an automatic mode, i.e. notably but in a non-limiting way:                colorimetric tests (both in one point and in the whole field of the display),        color uniformity test (histogram of colors . . . )        luminance measurements, which may also be carried out in the whole field of the display, uniformity tests may further be conducted in all the points of the field,        detection of faulty pixels (one or more pixels, clusters . . . ),        geometrical measurements (trace width, parallax, distortion . . . ),        detection of overlay of elementary patterns in an image . . .        
2. Description of the Prior Art
It is known that in the present state of the art, specific testing means are associated with each type of equipment being used for presenting information, which is particularly “expensive” if equipment has to be acquired involving display or viewing devices of different types.
Moreover, this extra equipment generates additional costs notably for the maintenance of the test means and management of obsolescence. Further, these test means frequently involve several sensors each assigned to a type of measurement carried out.
Thus, for a measurement of luminance, the sensor used will be a luminance meter; a colorimetric measurement will involve a colorimeter; for accurate measurements, a small field high resolution sensor will be used; for standard geometrical measurements, the sensor used will be a large field medium resolution sensor; certain measurements such as those relating to the detection of faulty pixels or to the analysis of elementary patterns, are usually conducted in a manual mode.
These drawbacks are again found in the inspection device descried in patent U.S. Pat. No. 6,064,462 which exploits the correlation between Newton rings formed at the surface of a liquid crystal display panel and the space between the two glass plates containing the liquid crystal, in order to check the uniformity of said space: this principle cannot be contemplated in a viewing device which does not use a liquid crystal display.
Also, Japanese patent JP 31 603 10 uses an assembly applying several photographic devices intended to take photographs of a test pattern shown on the cathode screen of an information presentation device. This assembly is specifically designed for a particular type of cathode screen and is not suitable for other display types such as head up displays or helmet mounted displays, for example.
Document WO 02/39 753 as for it, describes a device for testing liquid crystal display devices which uses light source means illuminating the display laterally as well as a photographic apparatus intended to receive, via a polarizer and a filter, a fraction of the light reflected by the display. A processor analyzes the image received by the photographic apparatus in order to check a certain number of criteria. This device is therefore specifically used for liquid crystal displays and is not suitable for the other types of displays.